Depositional%20Environments,%20Facies,%20Facies%20Models%20and%20Paleogeograpy - PowerPoint PPT Presentation
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Depositional%20Environments,%20Facies,%20Facies%20Models%20and%20Paleogeograpy
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Sediments accumulate in some environment of deposition or ... Stromatoporoid-tabulate coral reef facies. Facies Model. An idealized description of a facies ... – PowerPoint PPT presentation
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Title: Depositional%20Environments,%20Facies,%20Facies%20Models%20and%20Paleogeograpy
1
Depositional Environments, Facies, Facies Models
and Paleogeograpy
- Geologic History in Three Dimensions
2
Depositional Environments
- Sediments accumulate in some environment of
deposition or depositional environments - These areas receive net deposition
- Erosion may occur, but deposition dominates
- Features of these depositional environments are
preserved in the rock record - Examples
- Sediment texture
- Sedimentary structures (formed by processes in
the environment) - Fossils of organisms that lived in the
environment - Ancient environments can be reconstructed from
the clues that are preserved in the sedimentary
rocks
3
Depositional Environments
4
Facies
- All the properties of a body of rock that allow
us to differentiate it from those above, below
or laterally adjacent to it - Properties include
- Lithology rock type, including color, etc.
- Composition mineral content
- Texture grain size, sorting, roundness
- Sedimentary structures
- Fossils
- Facies means aspect same Latin root as face
- Overall appearance of a rock body
- Facies are the products of depositional
environments - Examples
- Planar laminated fine quartz arenite facies
- Bioturbated, poorly sorted muddy skeletal
limestone facies - Cross-stratified arkosic conglomerate facies
- Stromatoporoid-tabulate coral reef facies
5
Facies Model
- An idealized description of a facies
- Constructed from modern environments and ancient
rocks - Serves as a
- Norm for comparison
- Framework for observation
- Predictor of patterns
6
Facies Patterns
- Groups of facies commonly show patterns
- Proximal Facies (near the source) tend to be
coarse grained - Distal Facies (far from source) tend to be finer
grained - This pattern is displayed upstream and down in
rivers and onshore to offshore in coastal areas - Facies are arranged according to distribution of
depositional environments
7
Facies Migration
- Facies migrate through space and time
- Migration is in response to environmental factors
- Sediment supply
- Sea level change
- Subsidence
- Facies become stacked during migration
- A single facies is likely to be different ages in
different locations
8
Walthers Lawof the Correlation of Facies
- Only works where there are no unconformities
- Only facies that were laterally adjacent during
deposition (result of laterally adjacent
environments) can be stacked vertically - Vertical arrangement of facies gives us
information on - Distribution of environments
- How environments migrated through space and time
- Used as a basis to build facies maps or
paleogeographic maps - Accurate time correlation of facies is essential
- Time lines provide framework for correlation
- Bio-events
- Volcanic ashes
- Other thin, unique lithologies or marker beds
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Representing FaciesStratigraphic Sections
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Deltas
- Marginal Marine Deposition
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Ganges Delta, India
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Mississippi Delta (partial), USA
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Mississippi Delta (partial), USADrowning!
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Niger Delta 3D Model
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Modern Delta Subenvironments
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